Well, it would be technically possible to bring the Mil Horse into Zbrush and make a displacement map that would resemble the Phaedra.
I’m not sure how well such a map would hold up during movement of the figure.
It is beyond my meager capability and it would take a professional many hours (which they are unlikely to do for free).
The best solution is to model the horse from scratch and rig it inside the program you plan to use.
If you maintain certain proportions and groupings you may even be able to use the Mil Horse as a donor rig.
I know there are applications that enable one to extract the mesh object from a game. I do not know if this is legal for this game or any game for that matter.